The present invention relates to a magnetic bearing and coupling device and a scroll fluid machine including the same.
Scroll fluid machines such as vacuum pumps and compressors for treating toxic gases require that a gas does not leak from gas circulating paths for environmental protection. To meet the requirements, JP11-44297A discloses a magnetic coupling device in which the axial end of the eccentric shaft for supporting the orbiting scroll of the scroll fluid machine is covered with the cover, magnetic attractive force of the permanent magnets acting through the cover between the motor shaft and the eccentric shaft to allow the rotation of the motor shaft to be transmitted to the eccentric shaft without contact.
It is also necessary to reduce heat in the bearing of the eccentric shaft in view of operating efficiency. Thus, instead of a bearing in sliding contact with the outer circumferential surface of the eccentric shaft, it would be preferable to use a magnetic coupling that can support the eccentric shaft by magnetic repulsive force of magnets without contact.
However, when the magnetic bearing is used together with the magnetic coupling device as mentioned above, it would be necessary to install a number of permanent magnets for the magnetic bearing and magnetic coupling thereby increasing manufacturing costs. When the magnetic bearing is installed close to the magnetic coupling device, magnetic forces would affect each other to decrease its performance.